Document sdk-client

- Concepts: sdk-backend vs sdk-frontend vs sdk-client
- Guide (new section)
  - Basic scripts: get viewer
  - Auth: How to auth, reference the PAT
  - Plugin calls: Raw calls
  - Typing of plugins: With the new spec and download via npm
  - Graphql: raw graphql call
- Reference generated from typescript
- Small python reference / guide (community)
- Small golang reference / guide (community)